Operating a Catalytic Converter Device in a Motor Vehicle

ABSTRACT

Various embodiments may include a method for operating a catalytic converter device comprising: measuring electrical properties of the catalytic converter using high-frequency electromagnetic waves; determining a current operating state of the converter; acquiring reference points associated with the operating state; and checking a calibration of a measuring device. The operating states are selected from: an accumulator is completely emptied; an accumulator is completely filled; an accumulator is partially filled; a component to be stored is put into storage; a component to be stored is removed from storage; and an exhaust gas component to be converted or a quantity of the catalyst material in the exhaust gas which exceeds a threshold value is detected. The component to be stored is selected from the group consisting of: a catalyst material and the exhaust gas component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of International Application No. PCT/EP2017/069741 filed Aug. 3, 2017, which designates the United States of America, and claims priority to DE Application No. 10 2016 217 899.7 filed Sep. 19, 2016, the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to motor vehicles. Various embodiments may include methods for operating a catalytic converter device in a motor vehicle. The catalytic converter device can be, for example, an SCR (selective catalytic reduction) catalytic converter, a three-way catalytic converter, a diesel oxidation catalytic converter, and/or a particle filter as a catalytic converter device.

BACKGROUND

Catalytic converter devices are used to remove pollutants from the exhaust gas of motor vehicles. They are defined by the fact that they convert the pollutants by means of a catalyst material, wherein the catalyst material is not consumed in most cases. SCR catalytic converters are known, for example, from the document Guan et al.: “Review of state of the art technologies of selective catalytic reduction of NO_(x) from diesel engine exhaust”, Applied Thermal Engineering 66 (2014) 395-414.

Microwave measuring techniques have been used for some time for such catalytic converters, in order to determine the loading state of the catalytic converter during the operation of the motor vehicle. In this method, use is made of the fact that the metallic catalytic converter housing forms a cavity resonator in which microwaves can form resonances. For this purpose, microwaves are input into the catalytic converter housing with at least one antenna, and the position of resonance frequencies is determined in terms of transmission and/or reflection. The displacement of resonance frequency with respect to calibrated initial position can be used as a measure of the loading of the catalytic converter. However, in order to achieve a high level of precision for this measuring technology, the calibration of the measuring device must be reliable. In particular, it must be possible to detect effects produced by aging of the catalytic converter and/or by problems of the measuring device itself.

SUMMARY

The teachings of the present disclosure include methods for operating a catalytic converter device in a motor vehicle, with which methods electrical properties of the catalytic converter device can be determined with high-frequency support and with a particularly high level of reliability. For example, some embodiments include methods for operating a catalytic converter device in a motor vehicle, wherein the catalytic converter device converts at least one exhaust gas component, wherein electrical properties of the catalytic converter device are ascertained by means of a measuring device which detects the reflection and/or transmission of high-frequency electromagnetic waves which are input into a metallic housing of the catalytic converter device, wherein a calibration of the measuring device is checked using reference points, wherein the reference points are acquired in operating states of the catalytic converter device which are selected from the group of operating states comprising: an accumulator of the catalytic converter device is completely emptied of a component to be stored; an accumulator of the catalytic converter device is completely filled with a component to be stored; an accumulator of the catalytic converter device is partially filled with a component to be stored; a component to be stored is put into storage in an accumulator of the catalytic converter device; a component to be stored is removed from storage in an accumulator of the catalytic converter device; and/or an exhaust gas component which is to be converted by the catalytic converter or a quantity of the catalyst material in the exhaust gas which exceeds a threshold value is detected; wherein the component to be stored is selected from the group comprising a catalyst material and at least one exhaust gas component.

In some embodiments, the catalytic converter device is embodied as an SCR catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states comprising: the temperature of the catalytic converter device is above a defined threshold temperature; the temperature of the catalytic converter device is in the range for normal operation, and the catalytic converter device is heated; the temperature of the catalytic converter device is in the range for normal operation, and the catalytic converter device is cooled; and/or a breakthrough of NO_(x) or of the reducing agent NH₃ is detected.

In some embodiments, the catalytic converter device is embodied as a three-way catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states comprising: an oxygen accumulator of the catalytic converter device is completely emptied after a rich phase of an internal combustion engine of the motor vehicle; the oxygen accumulator is completely filled after the overrun mode of an internal combustion engine of the motor vehicle; oxygen is put into storage in the oxygen accumulator; oxygen is removed from storage in the oxygen accumulator; and/or a breakthrough of an exhaust gas component is detected.

In some embodiments, the catalytic converter device is embodied as an LNT catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states comprising: an NO_(x) accumulator of the catalytic converter device is completely filled; the NO_(x) accumulator is completely emptied after desulfurization; the NO_(x) is put into storage in the NO_(x) accumulator; the NO_(x) is removed from storage in the NO_(x) accumulator; and/or a breakthrough of NO_(x) is detected.

In some embodiments, the catalytic converter device is embodied as a diesel oxidation catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states comprising: the temperature of the catalytic converter device is below a defined threshold temperature; the temperature of the catalytic converter device is above a defined threshold temperature; and/or a breakthrough of an exhaust gas component is detected.

In some embodiments, the catalytic converter device is embodied as an ASC catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states comprising: the temperature of the catalytic converter device is above a defined threshold temperature; the temperature of the catalytic converter device is in the range for normal operation, and the catalytic converter device is heated; the temperature of the catalytic converter device is in the range for normal operation, and the catalytic converter device is cooled; and/or a breakthrough of an exhaust gas component or of an oxidizing agent is detected.

In some embodiments, the catalytic converter device is embodied as a particle filter, and the operating states in which the reference points are acquired are selected from the group of operating states comprising: the differential pressure at the particle filter is above a defined upper threshold temperature; and/or the differential pressure at the particle filter is below a defined lower threshold temperature.

In some embodiments, during the acquisition of reference points at least one of the following measurement variables is taken into account: the temperature of the catalytic converter device, gas humidity in the catalytic converter device, air mass flow through the catalytic converter device, metering quantity of a catalyst material to be metered in, gas composition of NO/NO₂in the exhaust gas, soot emissions, differential pressure at a particle filter.

The methods as described above may be used for diagnosing the catalytic converter device and/or diagnosing the measuring device.

DETAILED DESCRIPTION

Some embodiments include methods for operating a catalytic converter device which converts at least one exhaust gas component especially using at least one catalyst material, wherein electrical properties of the catalytic converter device are ascertained by means of a measuring device which detects the reflection and/or transmission of high-frequency electromagnetic waves which are input into a metallic housing of the catalytic converter device. High-frequency electromagnetic waves are understood to be electromagnetic waves in the range of microwaves, up to the range of >100 MHz to 20 GHz depending on the size of the catalytic converter.

In this context, a calibration of the measuring device may be checked using reference points. The reference points are acquired in operating states of the catalytic converter device which are selected from the group of operating states consisting of:

-   -   an accumulator of the catalytic converter device is completely         emptied of a component to be stored;     -   an accumulator of the catalytic converter device is completely         filled with a component to be stored;     -   an accumulator of the catalytic converter device is partially         filled with a component to be stored;     -   a component to be stored is put into storage in an accumulator         of the catalytic converter device;     -   a component to be stored is removed from storage in an         accumulator of the catalytic converter device; and     -   an exhaust gas component which is to be converted by the         catalytic converter or a quantity of the catalyst material in         the exhaust gas which exceeds a threshold value is detected.

In this context, the component to be stored is selected from the group comprising a catalyst material and at least one exhaust gas component. In some embodiments, the methods permit direct and particularly reliable determination of a loading state of a catalytic converter. In addition, they permit diagnosis of the catalytic converter device and of the measuring device. This ensures that the calibration of the measuring device is supported by reference points and checked at reference points. The reference points are suitably selected for this purpose.

At the first specified reference point, at which an accumulator of the catalytic converter device is completely emptied of a component to be stored, clear conditions apply with the complete emptying of the accumulator, since the loading state of the catalytic converter is precisely defined. Electrical properties of the catalytic converter device which are measured in this operating state can be compared directly with those of a calibration which was initially carried out. A change in the electrical properties, particular displacement of the resonance frequency or changing of the resonance quality, can then indicate, in particular, aging of the catalytic converter device.

At the second specified reference point, an accumulator of the catalytic converter device is completely filled with a component to be stored. A precisely known loading state of the catalytic converter is also present in this operating state. Electrical properties of the catalytic converter device which are measured in this operating state can also be compared directly with those of a calibration which was initially carried out. A reference point in an operating state in which an accumulator of the catalytic converter is partially filled with a component to be stored may also be useful, depending on the type of catalytic converter and the purpose of use.

At the fourth specified reference point, a component to be stored is put into storage in an accumulator of the catalytic converter device. This reference point is reached in an operating state of which it is known that under the present conditions the component to be stored is put into storage. At this reference point, electrical properties of the catalytic converter device are not considered in absolute terms, but rather their change as a reaction to the change in the loading state of the catalytic converter device is observed. An analogous procedure is adopted at the fifth specified reference point if a component to be stored is removed from storage in the accumulator of the catalytic converter device.

At the sixth specified reference point, an operating state is present in which an exhaust gas component which is to be converted by the catalytic converter or a quantity of the catalyst material in the exhaust gas which exceeds a threshold value is detected. A suitable sensor is used for detecting such slip. The detected slip is suitable for specifying an operating state with a precisely defined loading state of the catalytic converter device.

In some embodiments, the catalytic converter device comprises an SCR catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states consisting of:

-   -   The temperature of the catalytic converter device is above a         defined threshold temperature of, for example, 450° C. In this         operating state, there is no NH₃ stored in the catalytic         converter device, since in certain types of catalytic converter         desorption of NH₃ occurs at temperatures above 450° C. This         operating state is reached, for example, when a diesel particle         filter which is connected upstream of the catalytic converter         device is regenerated. In this operating state, the electrical         properties of the catalytic converter device are still         influenced by water which is bound in the catalyst. This effect         is dependent on the humidity of the gas, which can be determined         by means of the lambda value.     -   The temperature of the catalytic converter device is in the         range for normal operation, and the catalytic converter device         is heated. In this operating state, NH₃ is removed from storage,         i.e. the catalytic converter is discharged. In this context, the         removal from storage behavior of NH₃ is observed and correlated         with the temperature gradients, i.e. the heating rate of the         catalytic converter device.     -   The temperature of the catalytic converter device is in the         range for normal operation, and the catalytic converter device         is cooled. In this context, the catalytic converter is loaded         with NH₃ if urea is metered in. In this context, the putting         into storage behavior of NH₃ is observed and correlated with the         temperature gradient.     -   A breakthrough of NO_(x) or of the reducing agent NH₃ is         detected. A breakthrough which is measured with a suitable         sensor indicates a completely loaded or a completely emptied         catalytic converter.

The following effects can be utilized at the first specified reference point at which the temperature of the catalytic converter device is above a defined threshold temperature:

If urea is metered in and at the same time the catalytic converter is cooled from a temperature above, for example, 450° C., the aging of the catalytic converter can be inferred from displacement of the resonance frequency over time at a known temperature and known gas humidity level. Possible criteria for the aging here are the storage input behavior of NH₃ and the oxidation rate.

If metering of urea is started when an operating temperature of the catalytic converter is reached, the aging of the catalytic converter can also be inferred from the storage input behavior of NH₃.

If the internal combustion engine is switched off and the catalytic converter cools to a temperature below the dew point temperature, the time which passes after the starting of the internal combustion engine until the water is expelled is determined by means of high-frequency technology. The aging of the catalytic converter can then be inferred from displacement of the resonance frequency over time at a known temperature and gas humidity. Alternatively, after the metering in of urea has started, the time which passes until the water which has been put into storage at the storage locations of the catalytic converter has been replaced by ammonia can also be determined, and the aging of the catalytic converter can be inferred from displacement of the resonance frequency over time.

In this context, the ammonia concentration plotted against the degree of metering of the metering of urea is known or can be determined by means of a corresponding sensor system. In addition, the measurement can be assisted by the values of an exhaust gas sensor, for example of a NO_(x) sensor or NH₃ sensor.

In some embodiments, the catalytic converter device is embodied as a three-way catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states consisting of:

-   -   an oxygen accumulator of the catalytic converter device is         completely emptied after a rich phase of an internal combustion         engine of the motor vehicle;     -   the oxygen accumulator is completely filled after the overrun         mode of an internal combustion engine of the motor vehicle;     -   oxygen is put into storage in the oxygen accumulator     -   oxygen is removed from storage in the oxygen accumulator; and/or     -   a breakthrough of an exhaust gas component is detected, in         particular a breakthrough of hydrocarbons.

If the loading state of the catalytic converter is then selectively changed at the specified reference points by loading or discharging, changes of the measuring device can be inferred from displacement of the resonance frequency.

In some embodiments, the catalytic converter device comprises an LNT (Lean NO_(x) Trap) catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states consisting of:

-   -   a NO_(x) accumulator of the catalytic converter device is         completely filled;     -   the NO_(x) accumulator is completely emptied after         desulfurization;     -   NO_(x) is put into storage in the NO_(x) accumulator;     -   NO_(x) is removed from storage in the NO_(x) accumulator; and/or     -   a breakthrough of NO_(x) is detected.

If the loading state of the catalytic converter is then selectively changed at the specified reference points by loading or discharging, changes of the measuring device can be inferred from displacement of the resonance frequency.

In some embodiments, the catalytic converter device comprises a diesel oxidation catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states comprising:

-   -   the temperature of the catalytic converter device is below a         defined threshold temperature of typically 150° C.;     -   the temperature of the catalytic converter device is above a         defined threshold temperature of typically 150° C.; and/or     -   a breakthrough of an exhaust gas component is detected, in         particular a breakthrough of hydrocarbons or of hydrogen.

If the loading state of the catalytic converter is then selectively changed at the specified reference points by loading or discharging, changes of the measuring device can be inferred from displacement of the resonance frequency.

In addition, the NO->NO₂ conversion rate can be considered, wherein a reference point is acquired in an operating state in which the NO->NO₂ conversion rate exceeds a defined threshold value.

In some embodiments, the catalytic converter device is embodied as an ASC (ammonia slip catalytic converter) catalytic converter, and the operating states in which the reference points are acquired are selected from the group of operating states consisting of:

-   -   The temperature of the catalytic converter is above a defined         threshold temperature of, for example, 500° C. In this operating         state, the catalytic converter is not loaded.     -   The temperature of the catalytic converter device is in the         range for normal operation, and the catalytic converter device         is heated. Analogously to the procedure as was described for the         SCR catalytic converter, the storage removal behavior of ammonia         is observed in this operating state.     -   The temperature of the catalytic converter device is in the         range for normal operation, and the catalytic converter device         is cooled. In this operating state, as already described for the         SCR catalytic converter, the storage input behavior of ammonia         is observed.     -   A breakthrough of an exhaust gas component, in particular NH₃,         or of an oxidizing agent, is detected.

An analogous procedure can also be adopted when monitoring a diesel particle filter or Otto particle filter. In this context, a reference point can be acquired, in particular in the following operating states:

-   -   the differential pressure is above a defined upper threshold         temperature;     -   the differential pressure is below a defined lower threshold         temperature.

In this context, in the first mentioned operating state, filter generation is imminent, while in the second operating state, regeneration has just concluded, and therefore there is no loading with particles. Likewise, the start and the course of the removal of particles from storage and the putting into storage can be used as a reference.

During the acquisition of reference points, at least one of the measurement variables of the temperature of the catalytic converter, gas humidity in the catalytic converter device, air mass flow rate through the converter device, metering quantity of a metered-in catalyst material, gas composition of NO/NO₂ in the exhaust gas, soot emissions, and differential pressure at a particle filter may be taken into account. For this purpose, the measurement variables are monitored using suitable sensors, in particular using a temperature censor in the catalytic converter, using the lambda probe, using an air mass flow rate meter and using a unit which monitors the quantity of metered-in catalyst material, in particular urea. In some embodiments, influences of the specified measurement variables on the electrical properties of the catalytic converter device during the checking of the calibration can be taken into account so that said calibration becomes more precise.

In some embodiments, the methods described above may be used to diagnose the catalytic converter device and/or to diagnose the measuring device. In addition to the position of references, in this context, in particular, the storage input behavior and storage removal behavior of the catalytic converter devices is relevant for the assessment of, for example, the aging of the catalytic converter device: an aged catalytic converter exhibits a delayed storage input behavior and accelerated storage removal behavior. A reduced absolute storage capability of the catalytic converter also indicates aging. In a similar way, changes of an antenna of the measuring device, for example contamination as result of humidity or soot deposits, can be detected by means of a change in the resonance frequency. 

What is claimed is:
 1. A method for operating a catalytic converter device in a motor vehicle, wherein the catalytic converter device converts an exhaust gas component, the method comprising: measuring electrical properties of the catalytic converter device by detecting reflection and/or transmission of high-frequency electromagnetic waves emitted into a metallic housing of the catalytic converter device; determining a current operating state of the catalytic converter device; acquiring reference points associated with the determined current operating state; checking a calibration of the measuring device is checked using the reference points; wherein the operating states of the catalytic converter are selected from the group of operating states consisting of: an accumulator of the catalytic converter device is completely emptied of a component to be stored; an accumulator of the catalytic converter device is completely filled with a component to be stored; an accumulator of the catalytic converter device is partially filled with a component to be stored; a component to be stored is put into storage in an accumulator of the catalytic converter device; a component to be stored is removed from storage in an accumulator of the catalytic converter device; and an exhaust gas component which is to be converted by the catalytic converter or a quantity of the catalyst material in the exhaust gas which exceeds a threshold value is detected; wherein the component to be stored is selected from the group consisting of: a catalyst material and the exhaust gas component.
 2. The method as claimed in claim 1, wherein the catalytic converter device is comprises an SCR catalytic converter; and the operating states are selected from the group of operating states consisting of: the temperature of the catalytic converter device is above a defined threshold temperature; the temperature of the catalytic converter device is in the range for normal operation, and the catalytic converter device is heated; the temperature of the catalytic converter device is in the range for normal operation, and the catalytic converter device is cooled; and a breakthrough of NO_(x) or of the reducing agent NH₃ is detected.
 3. The method as claimed in claim 1, wherein the catalytic converter device comprises a three-way catalytic converter; and the operating states are selected from the group of operating states consisting of: an oxygen accumulator of the catalytic converter device is completely emptied after a rich phase of an internal combustion engine of the motor vehicle; the oxygen accumulator is completely filled after the overrun mode of an internal combustion engine of the motor vehicle; oxygen is put into storage in the oxygen accumulator; oxygen is removed from storage in the oxygen accumulator; and a breakthrough of an exhaust gas component is detected.
 4. The method as claimed in claim 1, wherein the catalytic converter device comprises an LNT catalytic converter; and the operating states are selected from the group of operating states consisting of: a NO_(x) accumulator of the catalytic converter device is completely filled; the NO_(x) accumulator is completely emptied after desulfurization; the NO_(x) is put into storage in the NO_(x) accumulator; the NO_(x) is removed from storage in the NO_(x) accumulator; and a breakthrough of NO_(x) is detected.
 5. The method as claimed in claim 1, wherein the catalytic converter device comprises a diesel oxidation catalytic converter; and the operating states are selected from the group of operating states consisting of: the temperature of the catalytic converter device is below a defined threshold temperature; the temperature of the catalytic converter device is above a defined threshold temperature; and a breakthrough of an exhaust gas component is detected.
 6. The method as claimed in claim 1, wherein the catalytic converter device comprises an ASC catalytic converter; and the operating states are selected from the group of operating states consisting of: the temperature of the catalytic converter device is above a defined threshold temperature; the temperature of the catalytic converter device is in the range for normal operation, and the catalytic converter device is heated; the temperature of the catalytic converter device is in the range for normal operation, and the catalytic converter device is cooled; and a breakthrough of an exhaust gas component or of an oxidizing agent is detected.
 7. The method as claimed in claim 1, wherein the catalytic converter device comprises a particle filter; and the operating states are selected from the group of operating states consisting of: the differential pressure at the particle filter is above a defined upper threshold temperature; and the differential pressure at the particle filter is below a defined lower threshold temperature;
 8. The method as claimed in claim 1, further comprising, during the acquisition of reference points, accounting for at least one of the following measurement variables: the temperature of the catalytic converter device, gas humidity in the catalytic converter device, air mass flow through the catalytic converter device, metering quantity of a catalyst material to be metered in, gas composition of NO/NO₂ in the exhaust gas, soot emissions, and differential pressure at a particle filter.
 9. The method as claimed in claim 1, further comprising diagnosing the catalytic converter device based on the calibration of the measuring device.
 10. The method as claimed in claim 1, further comprising diagnosing the measuring device based on the calibration of the measuring device. 